U.S. patent application number 14/379052 was filed with the patent office on 2015-09-03 for bypass circuit and wipe technique for contactor used to operate solid state relays that control heating elements.
The applicant listed for this patent is THE MIDDLEBY CORPORATION. Invention is credited to James Jeffery Hanson, Ricky Joe Sullivan McIntosh, William S. Schjerven, SR..
Application Number | 20150245623 14/379052 |
Document ID | / |
Family ID | 49161745 |
Filed Date | 2015-09-03 |
United States Patent
Application |
20150245623 |
Kind Code |
A1 |
Schjerven, SR.; William S. ;
et al. |
September 3, 2015 |
BYPASS CIRCUIT AND WIPE TECHNIQUE FOR CONTACTOR USED TO OPERATE
SOLID STATE RELAYS THAT CONTROL HEATING ELEMENTS
Abstract
A control circuit for a cooking oven. The control circuit
includes a contactor. The contactor has at least one contact and at
least one coil. A relay (such as a solid-state relay) is in series
connection with the contactor. A heating element is controlled by
the relay and is in series connection with the relay and the
contactor. The controller also includes a controller. The
controller is configured to bypass the relay and to control power
to the at least one coil.
Inventors: |
Schjerven, SR.; William S.;
(Schaumburg, IL) ; Hanson; James Jeffery; (Elgin,
IL) ; McIntosh; Ricky Joe Sullivan; (Altoona,
IA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE MIDDLEBY CORPORATION |
Eigin |
IL |
US |
|
|
Family ID: |
49161745 |
Appl. No.: |
14/379052 |
Filed: |
March 13, 2013 |
PCT Filed: |
March 13, 2013 |
PCT NO: |
PCT/US13/30680 |
371 Date: |
August 15, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61610939 |
Mar 14, 2012 |
|
|
|
Current U.S.
Class: |
219/414 ;
219/510 |
Current CPC
Class: |
H02H 3/05 20130101; A21B
1/40 20130101; H02H 5/04 20130101 |
International
Class: |
A21B 1/40 20060101
A21B001/40 |
Claims
1. A control circuit for a cooking oven, the control circuit
comprising: a contactor, the contactor including at least one
contact and at least one coil; a relay in series connection with
the contactor; a heating element controlled by the relay, the
heating element in a series-type configuration with the relay and
the contactor; and a controller configured to control a bypass of
the relay, and control power to the at least one coil.
2. The control circuit of claim 1, wherein the bypass of the relay
includes shorting the relay.
3. The control circuit of claim 1, wherein the contactor and
heating element are connected directly in series when the relay is
bypassed.
4. The control circuit of claim 1, wherein the bypass of the relay
and the power to the at least one coil creates an arc across at
least one contact.
5. The control circuit of claim 1, wherein the controller is
configured to control the bypass of the relay during startup of the
cooking oven.
6. The control circuit of claim 1, wherein the controller is
configured to control the bypass of the relay during shut down of
the cooking oven.
7. The control circuit of claim 1, wherein the controller is
configured to control the bypass of the relay upon activation of a
user bypass switch.
8. A cooking oven comprising: a housing; a heating element; and a
control circuit, including a contactor, the contactor including at
least one contact and at least one coil; a relay in series-type
configuration with the contactor and the heating element, the
heating element controlled by the relay; and a controller
configured to control a bypass of the relay, and control power to
the at least one coil.
9. The cooking oven of claim 8, wherein controlling a bypass of the
relay includes shorting the relay.
10. The cooking oven of claim 8, wherein the contactor and heating
element are connected directly in series when the relay is
bypassed.
11. The cooking oven of claim 8, wherein controlling a bypass of
the relay and power to the at least one coil creates an arc across
the at least one contact.
12. The cooking oven of claim 8, wherein the controller is
configured to control the bypass of the relay during the startup of
the cooking oven.
13. The cooking oven of claim 8, wherein the controller is
configured to control the bypass of the relay during shut down of
the cooking oven.
14. The cooking oven of claim 8, further including a user bypass
switch, wherein the controller is configured to control the bypass
of the relay upon activation of the user bypass switch.
15. A method for controlling a cooking oven, the cooking oven
including a housing and a heating element, the method comprising:
placing in a series-type configuration, a relay, a contactor
including at least one contact and at least one coil, and the
heating element; controlling a bypass of the relay; and controlling
power to the at least one coil; wherein the heating element is
controlled by the relay.
16. The method of claim 15, wherein controlling the bypass of the
relay comprises shorting the relay.
17. The method of claim 15, wherein the contactor and heating
element are connected directly in series when the relay is
bypassed.
18. The method of claim 15, wherein controlling the bypass of the
relay and controlling the power to the at least one coil creates an
arc across at least one contact.
19. The method of claim 15, further including controlling the
bypass of the relay during startup of the cooking oven.
20. The method of claim 15, further including controlling the
bypass of the relay during shut down of the cooking oven.
21. The method of claim 15, further including controlling bypass of
the relay upon activation of a user bypass switch.
22. A method of controlling a cooking oven having at least one
heating element and at least one contactor, the at least one
contactor having an associated coil, the method comprising:
receiving, at a controller, a signal from a user power switch;
generating, with the controller, a signal to activate one or more
first relays; shorting one or more second relays subsequent to
activating the one or more first relays; connecting the at least
one contactor directly in series with the at least one heating
element; energizing the coil of the at least one contactor; and
de-activating the one or more first relays.
Description
BACKGROUND
[0001] The present invention relates to heating circuits and, more
particularly, to heating circuits in conveyor ovens.
[0002] Electric heating elements are used in infrared cooking
ovens, including infrared conveyor ovens used to cook pizzas and
other foods. Electric heating elements can be controlled by
solid-state, zero-cross relays. In particular, the supply of
electrical power to the heating elements is controlled by the
relays. Electrical noise is generated when relay contacts open and
close and zero-cross relays generate less noise than other types of
relays. As with most components, solid-state relays are subject to
failure and if a relay fails in the on position, a constant supply
of power is provided to the heating element. This could lead to
over-heating and other hazards. A coil-activated or triggered
contactor can be used in the circuit prior to (or in series with)
the solid-state relays to provide a safety (or circuit break) in
case a solid-state relay fails in the on position. A
high-temperature-limit-control switch operates the contactor coil
and, if the high limit is tripped, the coil to the contactor is
de-energized and the contactor opens. When the contactor opens, the
supply of power to the heating element is interrupted.
SUMMARY
[0003] Recently, the materials used in contactors have changed. In
particular, the metal used for contacts in contactors has been
changed to silver. Silver replaced other metal for environmental
reasons. It is believed that silver contactors oxidize during
normal use of the conveyor oven. Once a contactor is contaminated,
such as by oxidation, the contamination creates a resistance high
enough to prevent power from flowing through the contactor; even if
the contacts of the contactors are in a closed position. Thus, the
electric heating elements do not receive power, and cannot cook
food.
[0004] In one embodiment, the invention provides a control circuit
for a cooking oven. The control circuit includes a contactor that
has at least one contact and at least one coil; a solid-state relay
in series connection with the contactor; and a heating element
controlled by the solid-state relay. The heating element is in
series connection with the solid-state relay and the contactor. The
controller is configured to bypass the solid-state relay, and
control power to the at least one coil.
[0005] In another embodiment, the invention provides a method for
controlling a cooking oven, the cooking oven including a housing
and a heating element. The method comprising placing in a
series-type configuration, a relay, a contactor including at least
one contact and at least one coil, and the heating element. The
method further comprising controlling a bypass of the relay; and
controlling power to the at least one coil; wherein the heating
element is controlled by the relay.
[0006] In another embodiment, the invention provides a method of
controlling a cooking oven having at least one heating element and
at least one contactor, the at least one contactor having an
associated coil. The method comprising receiving, at a controller,
a signal from a user power switch; generating, with the controller,
a signal to activate one or more first relays; shorting one or more
second relays subsequent to activating the one or more first
relays; connecting the at least one contactor directly in series
with the at least one heating element; energizing the coil of the
at least one contactor; and de-activating the one or more first
relays.
[0007] Other aspects of the invention will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of an infrared conveyor
oven.
[0009] FIG. 2 is a circuit diagram of an infrared conveyor oven
having a plurality of heating elements, solid-state control relays,
and two contactors.
[0010] FIG. 3 is a block diagram of a controller of an infrared
oven.
[0011] FIG. 4 is a flow diagram of a process for controlling the
temperature of an infrared oven.
[0012] FIG. 5 is a circuit diagram of an infrared conveyor oven
having a plurality of heating elements, two contactors, and a
high-amp bypass circuit.
[0013] FIG. 6 is a block diagram of the high-amp bypass
circuit.
[0014] FIG. 7 is a flow diagram of a process for controlling power
to a plurality of heating elements.
DETAILED DESCRIPTION
[0015] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways.
[0016] FIG. 1 is a perspective view of an infrared conveyor oven 1.
The conveyor oven 1 includes a housing 5 and conveyor 7. The
housing 5 encloses the electrical components 10 (shown in FIGS. 2
and 5) of the conveyor oven 1. The conveyor 7 is made of a metal
woven wire mesh and is used to transport food through the conveyor
oven 1. The conveyor 7 is coupled to a motor 11 (shown in FIGS. 2
and 5), which moves the conveyor 7 through the conveyor oven 1.
[0017] FIG. 2 is a circuit diagram illustrating the electrical
components 10 of the conveyor oven 1. The conveyor oven 1 generally
includes heating elements 15, solid-state control relays 20,
temperature sensors 25, contactors 30A and 30B, a temperature
switch 35, and a controller 40. In the embodiment shown, a power
supply 45 provides 230V AC voltage to the electrical components 10.
It is possible that the conveyor oven 1 and electrical components
10 could be designed to operate using a different power supply
voltage (and current). The heating elements 15, solid-state control
relays 20, and contactors 30A and 30B are connected in a
series-type configuration. In the embodiment shown, there are two
controllers 40, one controlling the upper set of heating elements,
and one controlling the lower set of heating elements. In the
embodiment illustrated, the controllers are substantially
identical.
[0018] The phrase "series-type configuration" as used herein refers
to a circuit arrangement where the described elements are arranged,
in general, in a sequential fashion such that the output of one
element is coupled to the input of another, but the same current
may not pass through each element. For example, in a "series-type
configuration," it is possible for additional circuit elements to
be connected in parallel with one or more of the elements in the
"series-type configuration." Furthermore, additional circuit
elements can be connected at nodes in the series-type configuration
such that branches in the circuit are present. Therefore, elements
in a series-type configuration do not necessarily form a true
"series circuit."
[0019] The heating elements 15 are electrical loads that produce
infrared light to produce heat. The heating elements 15 receive
power from the power supply 45 and, in the embodiment illustrated,
produce long-wave, infrared light to cook food.
[0020] The solid-state control relays 20 control the supplied power
to the heating elements 15 (and, thus, can be considered power
control relays). The solid-state control relays 20 are electronic
switching devices that switch the power to the heating elements 15
on or off. In some embodiments, the solid-state control relays 20
do not contain moving parts, thus minimizing any electrical noise
when switching the supplied power on or off. In other embodiments,
the solid-state relays 20 contain moving parts.
[0021] The contactors 30A and 30B further control the supplied
power to the heating elements 15. The contactors 30A and 30B act as
a safety, in case a solid-state control relay 20 fails. The
contactors 30A and 30B are electronic switching devices that
control the power to the heating elements 15, through the
solid-state control relays 20. The contactors 30A and 30B include
contacts and coils. When the coil is energized or powered, the
contacts close together, allowing current to flow to the heating
elements. If the coil is de-energized, the contacts are open, and
current is not supplied to the heating elements 15.
[0022] The temperature switch 35 senses the temperature of the oven
and controls the power to the coils. The temperature switch 35
provides power to the coils if the sensed temperature of the oven
is under a safety shutoff temperature (approximately 975.degree.
Fahrenheit). If the safety shutoff temperature is met, the
temperature switch 35 disconnects the power to the coils of the
contactors 30A and 30B opening the contacts, thereby cutting off
power to the solid-state relays 20 and heating elements 15.
[0023] FIG. 3 is a block diagram illustrating one of the
controllers 40. Each controller 40 includes a microcontroller 48
and a user interface 50. The microcontroller 48 includes a
processor 55 and memory 60. The processor 55 receives inputs from
the user interface 50 and temperature sensors 25. The processor 55
then executes software stored in the memory 60. The processor 55
(using the software) analyzes the received inputs and generates one
or more control signals that control the solid-state relays 20 and
motor 11.
[0024] At least one controller 40 controls the speed of the motor
11, and thus the speed of the conveyor 7. The controller 40
receives a user set cook time input from the user interface 60 and
controls the speed of the motor 11 based on the set cook time.
[0025] Each controller 40 further controls the temperature of the
conveyor oven 1. The temperature is based on a user set temperature
entered into the user interface 50. The controller 40 controls the
temperature by turning the solid-state relays 40 on or off which,
in turn, controls power (on or off) being supplied to the heating
elements 15. The controller 40 controls the solid-state relays 40
depending on the current temperature sensed by the temperature
sensors 25 as compared to the user set temperature.
[0026] FIG. 4 is a process 70 for controlling the temperature of
the conveyor oven 1, or more specifically, one set of the heating
elements 15 (either upper or lower). The process 70 is performed
when the controller 40 receives a user set temperature from the
user interface 50 (Step 71). The controller 40 then receives the
temperature of the conveyor oven 1 from the temperature sensors 25
(Step 72). The controller 45 then determines if the temperature of
the conveyor oven 1 is above the user set temperature (Step 73). If
the temperature of the conveyor oven 1 is above the user set
temperature, the controller 40 turns the solid-state relays 20 off,
thus cutting off power to the heating elements 15 (Step 74). If the
temperature of the conveyor oven 1 is not above the user set
temperature, the controller 40 turns the solid-state relays 20 on,
thus providing power to the heating elements 15 (Step 75). The
controller 40 then cycles back to Step 71.
[0027] FIG. 5 is a circuit diagram illustrating the electrical
components 10 of a conveyor oven 1 with a bypass controller 100.
The bypass controller 100 is a controller used at startup of the
conveyor oven 1 to create a burning arc across the contacts of the
contactors 30A and 30B. The arc burns away oxidation on the
contacts of the contactors 30A and 30B. Burning away contamination,
such as oxidation, is sometime referred to as "wiping" the contacts
or "cleaning" the contacts.
[0028] FIG. 6 is a block diagram illustrating the bypass controller
100 of the conveyor oven 1. The bypass controller 100 includes a
microcontroller 105. The controller 100 has an input 110 which is
connected to a user power switch 115. The controller 100 is also
connected to solid-state shorting relays 120, and provides commands
and similar signal on an output 125 connected to the controller 40.
In one embodiment, the microcontroller is a Microchip model number
PIC12F508 integrated circuit. The microcontroller 105 generally
includes a processor 130 and a memory 135. The processor 130
receives various inputs and executes a software program, stored in
the memory 135, for analyzing the received inputs, and generates
one or more control signals, or outputs. The user power switch 115
is the main power switch of the conveyor oven 1 and is located on
the user interface 50. The bypass controller 100 receives a signal
from the user power switch 115 (through input 110) when the
conveyor oven 1 is turned on or off. The bypass controller 100 is
electrically coupled to the coils of the contactors 30A and
30B.
[0029] The solid-state shorting relays 120, when activated, short
out the solid-state relays 20. In other words, when the shorting
relays 120 are turned on, a circuit path is created that bypasses
the relays 20. Thus, the controller 100 can be considered or viewed
as bypassing or shorting the relays 20. As discussed in greater
detail below, shorting the relays is a first step in a process
where contactors 30A and 30B are "wiped" or cleaned. Upon
completion of the "wipe" process, the bypass controller 100 sends a
signal to the controller 40 through output 125 to continue
operation of the oven, as is further discussed below.
[0030] At startup or shutdown the bypass controller 100 receives a
signal from the user power switch 115 at input 110. Upon receiving
either signal, the bypass controller 100 activates the solid-state
shorting relays 120. Activation of the shorting relays 120, shorts
out the solid-state relays 20. Once the solid-state relays 20 are
shorted out, the contactors 30A and 30B are connected directly in
series with the heating elements 15. The bypass controller 100 then
energizes the coils of the contactors 30A and 30B. Once the coils
are energized, the contacts of the contactors 30A and 30B close.
The heating elements 15 then draw a relatively large current
(approximately ten amps) through the contacts of the contactors 30A
and 30B. The ten amps of current create a burning arc across the
contacts. The arc "wipes" the contacts clean (or removes or reduces
the contamination, such as oxidation). The bypass controller 100
then de-activates the solid-state shorting relays 120, releasing
the short across the solid-state relays 20. The bypass controller
100 then sends a signal to the controller 40 through the output
125. In the case of startup, the controller 40 receives the signal
and begins normal operation of the conveyor oven 1. In the case of
shutdown, the controller 40 receives the signal and powers down the
conveyor oven 1. In another embodiment the bypass controller 100
performs the "wiping" process upon user activation or other
preprogrammed events. In such an embodiment, the conveyor oven 1
further includes a user bypass switch. Upon activation by a user,
the user bypass switch sends a signal to the bypass controller 100.
Upon receiving the signal, the bypass controller 100 performs the
"wiping" process.
[0031] FIG. 7 illustrates a process 200 for controlling the power
to the heating elements 15 upon startup. The process 200 is
performed when the conveyor oven 1 is powered on (Step 205). Once
the conveyor oven 1 is powered on and the bypass controller 100
receives the signal, the bypass controller 100 activates the
solid-state shorting relays 120 to short out the solid-state relays
20 (Step 210). The bypass controller 100 then powers the coils of
the contactors 30A and 30B, thus closing the contacts of the
contactors 30A and 30B (Step 215). The heating elements 15 draw
approximately ten amps of current through the contacts of the
contactors 30A and 30B, creating a burning arc across the contacts
(Step 220). The bypass controller 100 then releases the short
across the solid-state relays 20 (Step 225). The bypass controller
100 then sends a signal to the controller 40 to begin normal
operation of the conveyor oven 1, as discussed in process 70 (Step
230).
[0032] FIG. 8 illustrates a process 300 for controlling the power
to the heating elements 15 upon shutdown. The process 300 is
performed when the conveyor oven 1 is turned off (by the user or
otherwise), and a signal is sent to the bypass controller 100 (Step
305). Before powering down, the bypass controller 100 activates the
solid-state shorting relays 120 to short out the solid-state relays
20 (Step 310). The heating elements 15 draw approximately ten amps
of current through the contacts of the contactors 30A and 30B,
creating a burning arc across the contacts (Step 315). After a
predetermined period of time, the bypass controller 100
de-energizes the coils of the contactors 30A and 30B (Step 320).
The bypass controller 100 then de-activates the solid-state
shorting relays 120 (Step 325). The bypass controller 100 then
sends a signal to the controller 40 to power down the conveyor oven
1 (Step 330).
[0033] Thus, the invention provides, among other things, a bypass
circuit and wipe technique for contactors used to operate solid
state relays that control heating elements of a conveyor oven.
Various features and advantages of the invention are set forth in
the following claims.
* * * * *